All Amiga Keyboards are Amiga only. The 2000 and 3000 share keyboards. The 1000 and the 4000 are their own kind. None are compatible with AT keyboards. Same with mice.
I have never tried, but I thought the A4000T keyboard was similar to the A2000? Need to check when I get home now. The CDTV I picked up at the Swapmeet is definitely different (Mini Din.)
I would also pick up a Gotek floppy emulator for the A2000, as the drives are not compatible with anything and you need a working Amiga to make disks. With a Gotek you can load ADF (disk files) onto USB sticks and boot those as emulated floppies.
That is a good way to get access to boot floppies to get started. Without a Workbench disk he won't be able to boot to the CLI to get Amiga Explorer going. Also, Amiga Explorer seemed to have issues with higher serial speeds (above 19200? 38400?) for me but it is cool software. Would be really nice to see some cheap parallel port ethernet adapter that gets you to a file server. A few projects started but didn't go super far. If you are in a jam, I can copy Workbench floppies for ya on my 2500. I like the platform a lot but am not great at it. Been trying to repair a 600 but it has been kicking my butt. Need a replacement Fat Agnus IC for it for my next step in testing, the 2MB one that is more rare. - Ethan